1. Field of the Invention
The present invention relates to electrical sockets and connectors in general, and more particularly to a female holder or socket for a compact fluorescent lamp having two or more compact fluorescent tubes which share a common base, wherein the socket provides electrical connections and gripping means for the lamp base.
2. Description of the Related Art
Compact, super compact, or "Mini-" fluorescent lamps, known by many commercial names, such as Philips "PL", are rapidly gaining in popularity because they often provide as much light as a similar size incandescent lamp while requiring less than one-third the power and achieving 10 times greater service life.
These compact fluorescent lamps require sockets of unique design, in order to provide advantages to the user which may include various mounting methods to a surface, and rapid, safe, and easy wiring. These advantages are important with this type of lamp because with all connections made at a single base rather than at opposite ends of the common fluorescent tube, compact fluorescent lamps are finding application in space-saving lighting fixtures, ergonometric desk lamps, prefabricated or modular carrels and work stations, and cabinets, explosion-proof globes, and other single-end-access fixtures formerly requiring incandescent lamps.
In order to provide a wide range of sockets in large quantity and at low cost to meet expected demand, need for improvement in socket design for efficient, low-cost manufacture has become apparent.
Presently, sockets for smaller, compact fluorescent lamps, say of the 7-, 9-, and 13-watt sizes, typically are configured as a housing enclosure, usually constructed of two or more molded plastic parts, having a back wall and four side walls, open at one end to accept a relatively large lamp base member of a generally rectangular solid shape, such base member enclosing the starter and perhaps other elements of the electrical circuit of the lamp. Usually, the bottom and two, and frequently four, of the sides of the base member are closely contacted along their length by the sides or other surfaces within the housing to provide a high degree of lateral support for the lamp after it has been inserted within the housing. Additionally, the housing includes at least one side with an inward facing hook, or flange, of metal or plastic for establishing reversible gripping engagement with a retaining hook on the base of the lamp when the lamp is inserted in the housing, thus providing axial resistance against removal of the lamp. The lamp has two or more terminal pins, which terminal pins engage terminals in the housing in a sliding fit as the lamp base member is inserted into the housing. It can be seen that, with the smaller lamps having relatively large base members and a housing providing relatively large, solid support surfaces, the lamp is relatively securely retained in the housing, can be mounted in any orientation, and substantially resists removal from the housing.
With compact fluorescent lamps of larger wattage, for example the Philips "PL" 18-watt lamp, the starter and ballast elements are not included in a base member and, consequently, the base member is considerably smaller than it would otherwise be with a lower wattage lamp and, therefore, there is less surface for support within a conventionally designed housing. Known sockets for such lamps do not provide sufficient resistance against lamp removal to permit their use in any orientation without the need for additional supporting members apart from the lamp socket itself. Additionally, known sockets for such lamps frequently employ metal parts for gripping or other uses, which parts, of course, are subject to corrosion and thus may shorten the life of the sockets. Also, with some known sockets, electrically active parts are fairly readily accessible for contact by foreign objects.
Prior attempts to provide lamp sockets having such sufficient resistance against lamp removal are, for example, described in U.S. Pat. Nos. 4,643,503, issued Feb. 17, 1987, and 4,637,671, issued Jan. 20, 1987, both to Johnson, et al.
Patent '503 describes a socket device for a compact fluorescent lamp, which lamp comprises two tubes joined at one end to form a U-shaped lamp. The lamp has a coupling member or base at the other end thereof. The lamp base includes two opposed cross walls and opposed, semi-cylindrical end walls which encircle the outside areas of the lamp tubes and join the cross walls. At one end of the cross walls is an inner wall which is transverse to the cross walls and which grips two pairs of male electrical connecting prongs which are electrically connected to the ends of the lamp tubes. An outer wall, parallel to the inner wall, is located at the opposite end of the cross walls. The socket device includes a body wall having opposed inner and outer surfaces, with the inner surface parallel to the inner wall of the lamp base. The body wall forms two pairs of female electrical receptacles aligned in a row lateral the upper and lower cross walls at the inner surface adapted to receive the connecting prongs when the lamp base is inserted in the socket device. The socket device includes a support member comprising a support wall extending perpendicularly from the body wall to a position spaced directly below the lower cross wall of the lamp base. The support member also includes a pair of spaced, parallel support members connected to the support wall and extending though the space between the lower cross wall and the support wall for bearing contact with the lower cross wall. The body wall also defines a pair of elongated mating slots at the upper portion thereof at a position slightly spaced upward from the plane of the upper cross wall and from the female receptacles. The socket device includes a wire locking member with a biasable pair of spaced, parallel connecting portions that extend through the mating slots and springingly bear against the outer edges of the slots and are in gripping contact with outer surface of the body wall. The wire locking member also includes a pair of spaced, generally parallel supporting wire portions that extend from the connecting portions across, and in pressing contact with the upper cross wall, and terminate by forming a cross-wire portion that extends downwardly between the two tubes and in pressing, clamping association with the outer wall of the lamp base. The lamp is thus held against downward or upward transverse movement or tilting by the cooperation of the wire locking member and the parallel support members. Transverse movement of the lamp is resisted by the cooperation of the wire locking member and the connecting prongs inserted in the female receptacles. The wire locking member also resists removal of the lamp in the direction along the axis of the lamp.
Patent '671 describes a socket device identical to the device of Patent '503, except that the wire locking member has been replaced by a screw. Here, the screw extends through a threaded hole in an upper wall of the socket device, the upper wall extending transversely from the top of the body wall and over the upper cross wall of the lamp base. The screw bears against, and slightly deforms, the upper cross wall, thus securing the lamp in place. A locking washer is placed between the head of the screw and the upper surface of the upper wall. The cooperation of the screw, the support members, and the inner wall of the lamp base bearing against the inner surface of the body wall resist movement of the lamp in any direction.
Both of the abovedescribed sockets have inherent disadvantages when compared to the socket of the present invention. Each requires more parts than the present invention and, therefore, requires more complicated manufacturing processes. Additionally, if the wire and screw members are formed of metal, possibilities of corrosion problems exist. Also with each, it may be somewhat difficult to remove the lamp when either socket is mounted in certain orientations.
Another prior lamp socket device is described in U.S. Pat. No. 4,713,019, titled "Sockets for Compact Fluorescent Lamps, issued Dec. 15, 1987 to Edwin Gaynor. There, the socket comprises a back wall connected to four side walls, open at one end to accept the rectangular base of the lamp with the surfaces of the base closely contacting the inner surfaces of the back and side walls for support against transverse movement of the lamp. Removal of the lamp in the direction of the axis of the lamp is resisted by at least one inward facing hook on a side wall, the hook being shaped for establishing reversible locking engagement with a retaining hook on the lamp base. At least two such inward facing resilient flange hooks are preferred. While such a device is quite satisfactory for mounting and supporting therein a lamp of the type having a relatively large base, it is not satisfactory for mounting lamps of the type to which the present invention is directed.